This invention relates generally to a method and system for use in optical fiber technology. More particularly, this invention relates to an improved soldering method and system for manufacturing in-line micro-optic components.
In-line micro-optic component, such as isolators, gain flattening filters, wavelength division multiplexed (WDM) couplers, hybrid isolators and circulators, have been being widely employed in optical fiber technology. The performance, reliability and cost of the in-line micro-optic components depend heavily on their design and packaging technologies. Currently, two major kinds of design and packaging technologies are being widely employed in manufacturing the in-line micro-optic components and each kind has its own advantages and disadvantages. In applying a first kind of technology for designing and packaging the in-line micro-optic components, all optical parts are bonded together by applying epoxy bonding. The present inventor has filed several patent applications with new structural configurations and manufacturing methods for improving the in-line micro-optic components made by this first kind of technology using epoxy. In applying a second kind of technology for designing and packaging the in-line micro-optic components, both epoxy and solder bonding are applied to bond optical paths together. In the present invention, improvements over this second kind of technology are disclosed.
FIG. 1 is a cross sectional view to show the structure of a typical in-line micro-optic component manufactured according to the second kind of technology employing both epoxy and soldering. The in-line micro-optic component includes a pair of optical collimators 10 and 15. The pair of optical collimators can be a pair of single fiber optical collimators in the case of isolators and gain-flattening filters or a pair of a single fiber optical collimator and a dual fiber optical collimator in the case of WDM couplers and hybrid isolators. For the purpose of illustration, FIG. 1 shows a cross section view of a pair of single fiber optical collimators. The in-line micro-optic component further includes an optical core 20 attached to one of the optical collimators, i.e., the optical collimator 10 in FIG. 1, by applying a heat-curing epoxy 25. The optical core 20 has different inside structure and function for different in-line micro-optic components. For an example, in the case of isolators, the optical core is made of a Faraday rotator, two polarizers and a magnet, and will allow the transmission of optical signals in a direction while blocking the transmission of optical signals in the reverse direction. For another example, in the case of WDM couplers, the optical core is made of a thin-film interference filter and win combine or separate optical signals having different wavelengths. According to the conventional design and technology commonly applied, the pair of the optical collimators 10 and 15 with the optical core 20 are soldered together by using gold-plated stainless tubes. The optical collimator 10 with the optical core 20 and the optical collimator 15 are separately inserted and fixed into gold-plated stainless steel holders 30 and 35 by applying heat-curing epoxies 40 and 45. An optical alignment is carried out between the optical collimators 10 with the optical core 20 and the optical collimator 15 to achieve a lowest transmission loss from the input fiber 50 to the output fiber 55. These optical parts are soldered together through a gold-plated stainless steel holder 60 by applying a solder 65.
The conventional soldering method and system provides the in-line micro-optic components with good performance and reliability suitable for many types of applications. However, the conventional in-line micro-optic components have some disadvantages. First, in order to solder the optical collimators 10 with the optical core 20 and the optical collimator 15 together, three gold-plated stainless steel holders 30, 35 and 60 are needed. These three holders 30, 35 and 60, especially the holder 60, are produced at a relatively high price. Thus, the costs spent on these holders according to the structure and manufacturing method of the conventional in-line micro-optic components are high. Secondly, as shown by FIG. 1, there are ten soldering points for manufacturing an in-line micro-optic component according to the conventional soldering method and system. Soldering strength between these ten soldering points must be balanced to achieve a lowest transmission loss and the soldering process according to the conventional soldering method and system is complicated and time-consuming. Thus the labor costs of the conventional in-line micro-optic components are also high. Thirdly, while optical system designers and operators prefer to have compact in-line micro-optic components, the sizes of the conventional in-line micro-optic components cannot be made compact due to the limited size of the holder 60. Thus, further development of compact low-cost in-line micro-optic components is limited by these difficulties.
Therefore, a need still exists in the art of design and packaging of the in-line micro-optic components to provide improved material compositions, soldering configuration, device structure, and manufacturing processes to overcome the difficulties discussed above. Specifically, a technique to provide the in-line micro-optic component with compact size and low cost is required.
It is therefore an object of the present invention to provide an improved design and process for fabricating an in-line micro-optic component without requiring an outer holder and multiple soldering points. This present invention provides a simplified in-line micro-optic component configuration that can be manufactured with lower cost and reduced size. Thus, the aforementioned difficulties and limitations in the prior art can be overcome.
Specifically, it is an object of the present invention to provide a design and process to solder the in-line micro-optic components together by employing only the inner holders without requiring an additional outer holder commonly used in the conventional in-line micro-optic component manufacturing processes. Two gold-plated stainless steel holders are used in the soldering process to lower the cost and reduce the size by eliminating the requirement of a third, expensive holder. As a result, the in-line micro-optic components produced according to the new soldering method and system of this invention have lower cost and smaller size. Therefore, the in-line micro-optic components of this invention can be employed in fiber optic technology for broadened applications with being less limited by the cost and size problems of the in-line micro-optic components as those encountered in the prior art.
Briefly, in a preferred embodiment, the present invention discloses an in-line micro-optic component. The in-line micro-optic component includes an optical core attached to a first optical collimator by applying a first heat-curing epoxy. The in-line micro-optic component further a first gold-plated stainless steel holder holding the first optical collimator. The first optical collimator is inserted and fixed in the first stainless steel holder by applying a second heat-curing epoxy. The in-line micro-optic component coupler further includes a second optical collimator. The in-line micro-optic component coupler further includes a second gold-plated stainless steel holder holding the second optical collimator. The second optical collimator is inserted and fixed in the second stainless steel holder by applying a third heat-curing epoxy. After the optical alignment between the first optical collimator with the optical core and the second optical collimator is done to achieve a lowest transmission loss, the first and second stainless steel holders are soldered together.
The present invention further discloses a method for fabricating an in-line micro-optic component. The method includes the steps of: a) attaching an optical core to a first optical collimator by applying a first heat-curing epoxy; b) inserting and fixing the first optical collimator with the optical core into a first gold-plated stainless steel holder by applying a second heat-curing epoxy; c) inserting and fixing a second optical collimator into a second gold-plated stainless steel holder by applying a third heat-curing epoxy; d) mounting the first optical collimator with the optical core and the second optical collimator on an alignment stage then adjusting a relative position of the first optical collimator with the optical core to the second optical collimator until a lowest transmission loss is achieved; and e) soldering the first and second stainless steel holders together.